Numpy: extract data and coordinates from 2-D arrays

Question

Given:

M = [[1, 2],
     [3, 4]]

N = [[(0,1), (1, 0)],
     [(1,1), (0,0)]]

With M and N, both of dimension 2x2. How might I get a list L, of tuples, where each tuple is the combination of the position of the value, and the values from M and N:

L = [((0,0), (0,1), 1) ...]

Where the first entry above in L, is the position (0,0) in M and N, and the tuple/value (0,1) from N, and the value 1 from M.

Do I need to stack M, N to create a third dimension? And does numpy have a clean and efficient way to produce such a list of tuples?

Yes, that makes it 3d. Try using printing np.array(N).shape to see. In any case, why do you need the position in L? I mean it seems like saving L as an array where L[0][0]=((0,1),1) would be nicer instead of saving the indices. — kabanus
– kabanus, Commented Oct 28, 2016 at 12:10
The elements in L just map the index to the values. That is no additional information if you already have M and N, since you can just index M and N directly without storing the mapping, so you don't need L at all. What exactly are you trying to do? — Jan Christoph Terasa
– Jan Christoph Terasa, Commented Oct 28, 2016 at 12:53

Kennet Celeste · Accepted Answer · 2016-10-28 13:57:04Z

1

use this:

zip(*[iter(([((row,col),N[row][col],M[row][col]) for row in range(2) for col in range(2)]))]*2)

result:

[(((0, 0), (0, 1), 1), ((0, 1), (1, 0), 2)),
 (((1, 0), (1, 1), 3), ((1, 1), (0, 0), 4))]

edited Oct 28, 2016 at 13:57

answered Oct 28, 2016 at 12:06

Kennet Celeste

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3 Comments

hpaulj Over a year ago

What difference does np.array make? This just list code.

Kennet Celeste Over a year ago

@hpaulj Well actually in my code I used list at last, but I forgot to copy it here. I just summarized my code. Thanks for mentioning

hpaulj Over a year ago

I wonder if the OP really has arrays. N looks more like a nested list that np.array would turn into a 3d array.

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